In recent years, in addition to increasing the storage capacities of storage apparatuses and managing data stored in storage apparatuses independently, an operating mode of storage apparatuses has gained an attention wherein multiple storage apparatuses are collectively operated as a single storage apparatus (system), for managing and manipulating data.
In order to realize such an operating mode, storage apparatuses preferably exchange information on resources managed by those storage apparatuses at regular intervals. The information to be exchanged includes, for example, the status of storage devices, information indicating whether or not the storage devices are accessible, and information indicating connection paths between the storage devices and whether or not the connection patties are connectable.
When resource management information is updated in a storage apparatus, for example, storage apparatuses can share resource management information of local and other storage apparatuses, by exchanging all resource management information including the updated information, with each other.    Patent Document 1: Japanese Laid-open Patent Publication No. 2002-120417    Patent Document 2: Japanese Registered Patent Publication No. 62-36574
There is some time delay before updated resource management information is distributed to all storage apparatuses in a system after the resource management information is updated in a storage apparatus. Depending on the timing when a storage apparatus attempts to look up the resource management information of other storage apparatuses, the old resource management information may be looked up instead. In such a case, the storage apparatus may operate based on the old resource management information that does not reflect the current configuration of the other storage apparatus, which may adversely affect the operation of the system.
One solution to prevent old resource management information from being looked up is that a storage apparatus attempting to look up resource management information of other storage apparatuses inquires whether or not the resource management information has been updated, by sending the resource management information possessed by the inquiring storage apparatus, for example. If the resource management information has been updated, the inquiring storage apparatus can obtain new resource management information from other storage apparatuses, and look up the information.
Resource management information is relatively large in size, however. Hence, if resource management information is sent every time other storage apparatuses attempt to utilize the resource management information, an increase in the communication data volume may be induced, which might induce a reduced performance of the system.
The above-described disadvantage is not limited to storage systems. For example, such a disadvantage may also be experienced in a wide variety of information processing systems wherein multiple control apparatuses share management information with each other, such as systems wherein multiple monitor apparatuses exchange monitor information about targets to be monitored.